The currently described disclosure relates to use of service numbers to protect against text message spoofing (e.g., spoofing of Short Message Service (SMS) messages). Various software applications allow the exchange of SMS messages between users. During use of such software applications, a user is generally identified by his/her mobile phone number, which can appear in the “from” field of a text message header and thereby identify the origin of the text message (i.e., the sender's “user number”). Because some known methods of text messaging (e.g., SMS) are not fully secure, there is often no simple way to validate the origin of a text message. In some instances this security gap makes it possible for an individual to misrepresent (i.e., “spoof”) the sender of a text message. In this manner, the unauthorized user is able to successfully send text messages that appear to come from a number not owned or controlled by the unauthorized user. A need therefore exists for improved methods and systems for protecting against text message spoofing.